Chemical composition of kabuli and desi chickpea (Cicer arietinum L.) cultivars grown in Xinjiang, China

Abstract Chickpeas are a very important legume crop and have abundant protein, carbohydrate, lipid, fiber, isoflavone, and mineral contents. The chemical compositions of the four chickpea species (Muying‐1, Keying‐1, Desi‐1, Desi‐2) from Xinjiang, China, were analyzed, and 46 different flavonoids in Muying‐1 were detected. The moisture content ranged from 7.64 ± 0.01 to 7.89 ± 0.02 g/100 g, the content of starch in the kabuli chickpeas was greater than that in the desi chickpeas, the total ash content ranged from 2.59 ± 0.05 to 2.69 ± 0.03 g/100 g and the vitamin B1 content of the chickpeas ranged from 0.31 to 0.36 mg/100 g. The lipid content ranged from 6.35 to 9.35 g/100 g and the major fatty acids of chickpeas were linoleic, oleic, and palmitic acids. Both kabuli and desi chickpeas have a high content of unsaturated fatty acids (USFAs), Muying‐1 and Desi‐1 contained the highest level of linoleic acid, and Keying‐1 had the highest oleic acid content. The protein level ranged from 19.79 ± 2.89 to 23.38 ± 0.30 g/100 g, and the main amino acids were aspartic acid, glutamic acid, and arginine acid. The four chickpea species had significant amounts of essential amino acids (EAAs). Forty‐six varieties of flavonoids in Muying‐1 were determined by ultra high‐performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC‐QqQ‐MS) analysis, and there were higher levels of conjugate flavonoids (55.95%) than free flavonoids (44.05%). Isoflavones were the most abundant flavonoids in Muying‐1, and among the isoflavones, daidzin had the highest content, followed by biochanin A and genistin. Muying‐1 was rich in daidzin, biochanin A, genistin, troxerutin, isorhamnetin, astilbin, L‐epicatechin, astragalin, acacetin, hyperoside, and myricitrin. Information provided in the study will be helpful to further understand the chemical composition of chickpeas and be beneficial to the development of chickpeas.


| INTRODUC TI ON
Chickpea (Cicer arietinum L.) is an ancient pulse crop and is the world's third most essential food legume, as it is currently cultivated in over 13.7 million hectares, with an annual production of 14.3 million tons in 2019 (FAOSTAT, 2021). Chickpea is used as a highenergy and protein source in human diets and is widely consumed because of its high nutritional value (Gao et al., 2015).
Chickpeas mainly come in two varieties, namely, kabuli and desi types. In general, the surface of the kabuli chickpea has a beige coat and it is a large seed without edges, while the desi chickpea has a darkcolored coat over small and rough seeds (Mohammadi, 2015). Summo et al. (2019a) pointed out that different cultivated chickpea cultivars had different physicochemical, nutritional, and functional properties.
For example, brown chickpeas could be used to make vegan burgers or bread and meat extenders, while beige chickpeas had better functional properties and applications in other food products. Both desi and kabuli chickpeas are rich in starch, proteins, carbohydrates, lipids, fibers, flavonoids, and micronutrients such as zinc, iron, and manganese, which are commonly used in the prevention and treatment of chronic diseases such as diabetes and hyperlipidemia.
Legumes are known for their high protein content and chickpea is the cheapest source of protein for the poor people, economically weaker families, and vegetarians (Kaur & Prasad, 2021). Chickpea has potential use as a source of protein, carbohydrates, minerals, and many other important nutrient sources. Chickpea has significant amounts of all of the essential amino acids (EAAs) (Yegrem, 2021).
Chickpea protein has advantages of high production volumes, low cost, excellent balance in the composition of essential amino acid, high bioavailability, and low allergenicity compared to soybeans (Boukid, 2021). Wang et al. (2010) found that compared with soybean protein isolates, Chinese kabuli and desi chickpea protein isolates had higher digestibility values.
It has been reported that the content of total starch in chickpea seeds is as high as 40%-60%, approximately 52.5 g/100 g, of which 35% is resistant starch and the remaining 65% is available starch (Aguilera et al., 2009). The total lipid content of chickpea is 4.5-6.0 g/100 g (Boye et al., 2010). The total dietary fiber (DF) content of chickpea is 18-22 g/100 g, and the dietary fiber (DF) concentration is more than twice that of cereal or oilseed bean (Chen et al., 2016).
Chickpea is reported to be a good source of iron and it contains a higher level of iron in comparison with other legumes (Abebe et al., 2006).
Chickpeas also contain a large number of biologically active molecules, including steroids, flavonoids, and terpenes, which play an important role in maintaining human health. Chickpea is an important source of flavonoids in human diet. The majority of the flavonoids and phenolics present in chickpea are concentrated mainly in the seed coat and the levels of these compounds are 11, 13, and 31 times (flavonoid, total phenolic, and antioxidant activity, respectively) greater in brown Desi type as compared to creamish Kabuli type (Kaur & Prasad, 2021).
In addition, isoflavones, a large group of plant secondary metabolites belonging to the molecular class of flavonoids, are important components in legumes that exhibit strong antiestrogenic, antioxidative, and antimicrobial activities (Zhao et al., 2009). Isoflavones also presented cancer prevention due to nonhormonal mechanisms, and these compounds suppress angiogenesis, induce apoptosis, and inhibit DNA topoisomerases and cancer cell differentiation (Dulce-María et al., 2021). The NAD + /NADH (nicotinamide adenine dinucleotide) redox imbalance and mitochondrial complex I dysfunction in the pancreas of type 2 diabetes mellitus (T2DM) rats were corrected by chickpea flavonoids (Fu et al., 2022). In naturally occurring glycosidic form, isoflavones are conjugated at the 7′ position and are often esterified with acetyl or malonyl groups at the 6′ position of the sugar residue (Taylor et al., 2005). Konar et al. (2012) reported that chickpeas may serve as an alternative to soy because they are a significant source of isoflavones (3078 ± 372 μg/kg total content) and are also rich in biochanin A. Shang et al. (2019) reported that the yields were 0.55, 1.56, 1.71, 2.40, and 8.35 mg/g for ononin, sissotrin, formononetin, biochanin A, and total flavonoid content, respectively, in chickpea sprouts. The content of total isoflavones in germinated chickpea was about 5 times of that in germinated soybean (Wang et al., 2021).
At present, the cultivated area of chickpea in Mulei County of Xinjiang has exceeded 0.67 million hectares, accounting for 83% of the total planted area of chickpea in China. Muying-1 chickpea is the main cultivated variety in Xinjiang because of its high yield, good taste, and remarkable economic benefits. Keying-1, Desi-1, and Desi-2 chickpeas are also grown in Mulei County, but Keying-1 is less stable than Muying-1, and the two Desi type chickpeas' color, taste, processing performance, and powder yield are inferior to those of Kabuli type chickpeas, so the cultivation of Keying-1, Desi-1, and Desi-2 chickpeas gradually declines. Further insights into the chemical compositions of the four chickpea species in Mulei County of Xinjiang could make their beneficial effects widely known and better support their cultivation and marketing. The purpose of this study was to determine the chemical composition and flavonoids of chickpeas and lay a better foundation of chickpea utilization. With this premise, the mean concentrations of moisture, protein, fat, starch, ash, minerals, and vitamin B 1 of the four chickpea species Muying-1, Keying-1, Desi-1, and Desi-2 from Mulei County in Xinjiang were determined. The amino acid composition and fatty acid composition of the four chickpea species were analyzed, and the flavonoids of Muying-1 chickpea samples were determined by ultra highperformance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-QqQ-MS).

| Chemical composition analysis
The ash content, vitamin B 1 content, moisture level, and total crude protein (nitrogen factor of 6.25) were determined according to the AOAC (Association of Official Analytical Chemists) official method (AOAC, 2006). The lipid content was determined by means of a Soxhlet apparatus using petroleum ether as the extracting solvent.
The minerals, such as magnesium, zinc, and iron, were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The total starch content was measured using the enzyme hydrolysis method (Rayo-Mendez et al., 2019).

| Amino acid analysis
The amino acids of chickpea flour were determined using an automatic amino acid analyzer (S433D, Sykam, Germany) according to the Chinese Standard (GB 5009.124-2016) (2016a).
The sample (0.5000 g) was hydrolyzed with 10 ml 6 mol/L HCl in an evacuated test tube for 24 h at 105°C. The hydrolyzed solution was filtered using a membrane with a pore size of 0.22 μm. The mobile phase was a 0.2 mol/L pH 2.2 citric acid sodium-buffering system. The amino acid composition was expressed as gram (g) of amino acids per 100 grams of chickpea flour and calculated in Eq.
The experimental data were from three replications.
where X represents the amino acid content of the samples, g/100 g; c represents the concentration of the amino acid in the sample, nmol/ mL; F represents the sample dilution ratio; V represents the constant volume of the sample after hydrolysis, ml; M represents the molecular weight of each amino acid; m represents the sample weight, g; 10 9 represents the coefficient of converting the sample content from nanograms (ng) to grams (g); and 100 represents the conversion factor.

| Fatty acid analysis
The fatty acid composition of chickpea was determined by gas- The GC-MS analysis was performed with an Agilent 7890B/5977A gas chromatograph mass spectrometer system equipped with a DB-5MS capillary column (30 m long; 0.25 mm i.d.). Helium was utilized as carrier gas at a constant flow rate of 1.0 ml/min. The oven temperature program was as follows: 5 min at 60°C, ramped from 60 to 230°C at 3°C/min, and 5 min at 230°C; then, ramped from 230 to 280°C at 20°C/min, and 3 min at 280°C. The injection mode was splitless, the injector temperature was 280°C, and the ionization voltage was 70 eV.

| Flavonoid analysis by UPLC-QqQ-MS
Chickpea flour (2.0000 g) was defatted by homogenization with petroleum ether (solid/liquid ratio of 1:10 g/ml) at room temperature for 12 h. Then, the defatted samples were extracted with 70% ethanol (solid/ liquid ratio of 1:20 g/ml) for 4 h at 70°C. Next, the extracts were filtered and concentrated with a rotavapor device. Finally, the crude chickpea flavonoid extract (CCFE) was obtained using vacuum freeze drying. CCFE (0.2000 g) was mixed with 0.8 ml of 80% methanol (MeOH), and the mixture was sonicated for 0.5 h at 4°C to extract the components. The solution was allowed to stand for 60 min at 4°C and then centrifuged for 10 min. The residues were reconstituted in 0.4 ml of 80% (v/v) aqueous MeOH (including an internal standard at 200 ng/mL) and shaken for 5 min. The solution was kept at 4°C for 60 min and then centrifuged for 10 min, and the supernatant was collected and injected into the UPLC-QqQ-MS system.

| Statistical analysis
Data from the different experiments were recorded as the means ± standard deviation (SD) of triplicate measurements and were analyzed by SPSS 26.0 software (SPSS, Inc., Chicago, IL, USA).
The results were submitted to analysis of variance (ANOVA) and Duncan's multiple range test for means comparison at (p < 0.05) significance was applied.
Importantly, the differences in the moisture content were significant, providing an important parameter to be considered during seed storage.
The protein content in chickpeas ranged from 19.79 ± 2.89 (Muying-1) to 23.38 ± 0.30 g/100 g (Keying-1). There were significant differences in the protein content between Muying-1 and Keying-1 (p < .05) and between Desi-1 and Desi-2 (p < .05). However, there were no significant differences in protein content between Muying-1 and Desi-2 or Keying-1 and Desi-1. Generally, the crude protein content of the different chickpeas represents 12% to 30% of the seeds, with an average value that is commonly 2-3 times higher than that of cereal grains (Wood & Grusak, 2007). In this study, the average amounts of protein from the Muying-1, Keying-1, Desi-1, and Desi-2 were higher than that from Merella chickpeas (15.70 g/100 g) (Landi et al., 2021) and other legumes such as common bean and Bambara groundnut accessions (Baptista et al., 2017). Several studies have reported that true protein digestibility, biological value, net protein utilization, and protein efficiency ratio of chickpeas are higher than those of most legumes including soybeans (Dadon et al., 2017;Khan et al., 1979;Liu et al., 2008).
The lipid content of four chickpea species was determined to range from 6.35 ± 1.65 to 9.35 ± 2.00 g/100 g. There was no significant difference in lipid content between Muying-1, Keying-1, Desi-1, and Desi-2 (p ≥ .05). Summo et al. (2019b) reported that considering the seed coat color, beige chickpeas showed the highest lipid content, followed by black chickpeas and brown chickpeas. The lipid content of foods is often responsible for their flavor, which in the case of chickpea may contribute to its "nutty" taste (Yegrem, 2021).
On a weight basis, the same amount of lipids provides more than twofold the energy generated by the intake of proteins and carbohydrates (Camargo et al., 2019). Camargo et al. (2019) reported that in this sense, due to its lower lipid content (up to twenty-one-fold less) compared to that of soybean, chickpea stands out as a good option in weight management.
The starch content in chickpeas ranged from 27.15 ± 1.19 to 36.22 ± 0.55 g/100 g; the values of Muying-1 and Keying-1 were the highest, while that of Desi-1 was the lowest. A significant difference was found in the starch content among the four chickpea species, and the contents of starch in kabuli chickpeas (Muying-1, Keying-1) were greater than those in desi chickpeas (Desi-1 and Desi-2) (p < .05).
These results were similar to an investigation by Miao et al. (2009), which showed that the starch contents of kabuli and desi chickpeas were 37.9% and 29.7%, respectively. Kaur et al. (2019) reported that the total starch content in chickpea genotypes ranged from 26.49% to 39.27% with a mean value of 31.43%. The significant differences in the ash content of chickpeas have an important role in mineral resources. The Keying-1 variety had the highest total ash content, while Desi-2 had the lowest ( Table 2).
No significant differences were found in the total ash contents among Muying-1, Keying-1, and Desi-1 (p ≥ .05), but there was a significant difference in the ash content of Desi-2 compared with those of the other three chickpeas (p < .05). The ash contents in Muying-1, Keying-1, Desi-1, and Desi-2 were lower than those reported in Merella (3.50 g/100 g) and Alta Valle di Misa (4.0 g/100 g) (CREA, 2020).
The different mineral contents of the chickpeas are shown in Table 2. The zinc, iron, and magnesium contents in Muying-1, Keying-1, Desi-1, and Desi-2 ranged from 3.61 mg/100 g to 5.33 mg/100 g, from 5.49 mg/100 g to 9.72 mg/100 g, and from 197.73 mg/100 g to 230.52 mg/100 g, respectively. No significant difference was found among the mineral contents of the chickpea strains in this study (p ≥ .05). The mineral contents in the four chickpea cultivars were higher than those of desi chickpea cultivars grown Thavarajah and Thavarajah (2012) reported that Zn and Fe contents in chickpea cultivars ranged from 3.7 mg/100 g to 7.4 mg/100 g and from 4.6 mg/100 g to 6.7 mg/100 g, respectively. These results indicated that chickpea might provide a sufficient amount of minerals to meet the human mineral requirements.
Muying-1 had a significantly higher content of vitamin B 1 than the other chickpea species.

| Amino acid composition analysis
The amino acid composition of the four chickpea species is shown in Essential amino acids (EAAs) are indispensable nutrients for the human body and must be obtained from the diet because they are not synthesized by the human body. As shown in Table 3, chickpea had significant amounts of all of the EAAs. A significant difference in EAA contents was found between Keying-1 (8.03 g/100 g) and Desi-2 (6.92 g/100 g) (p < .05). The contents of EAA in the four chickpea species were higher than those in field peas (Pisum sativum L.) (6.62 g/100 g) and hull-less barley (3.23 g/100 g) (Bai et al., 2018;Witten et al., 2018). In addition, the amounts of EAAs in Muying-1 and Keying-1 chickpeas were also higher than those in Valle Agricola chickpeas (7.12 g/100 g) determined by Landi et al. (2021).
The ratios of EAA to NEAA (nonessential amino acid) in Muying-1, Note: Data were expressed as mean ± SD (n = 3). Values in the same column with different superscript letters represent significant differences between varieties at p < .05.

| Fatty acid composition analysis
The fatty acid composition of the four chickpea species is shown in The fatty acid profile of all chickpea cultivars reveals their lipids are a good source of nutritionally essential linoleic and oleic acids.
The nutritional value of linoleic acid is due to its metabolism at the tissue level, which produces hormone-like prostaglandins. The activity of these prostaglandins includes the lowering of blood pressure and the constriction of smooth muscle (Aurand et al., 1987).
Linoleic and linolenic acids are the most important essential fatty TA B L E 3 Amino acid composition (g/100 g chickpea flour) in four varieties of chickpeas acids required for growth, physiological functions, and maintenance (Pugalenthi et al., 2004). Jukanti et al. (2012) also confirmed that chickpea consumption, in particular the black type, could help to enhance the dietary intake of healthy and nutritionally essential fatty acids such as linolenic and linoleic acids. The differences among the strains may be that the maturation and environmental conditions of the chickpeas were different (Deng et al., 2018). Dadon et al. (2017) reported that the fatty acid content of chickpeas is influenced by the genotype (cultivar effect), the environment (i.e., growing seasonal profile, edaphic and climatic factors, pests, diseases), and their possible genotype x environment (G x E) interaction. Gul et al. (2008) reported that chickpea planted in autumn had 35% and 63% oleic acid and linoleic acid, respectively, whereas spring chickpea had oleic acid and linoleic acid of 18% and 47%, respectively.
Moreover, the USFA/SFA ratio indicated that chickpeas contained more USFA, which has important nutritional and health implications, since the consumption of unsaturated fatty acids is highly recommended to reduce the risk of cardiovascular diseases. Note: Data were expressed as mean ± SD (n = 3). Values in the same column with different superscript letters represent significant differences between varieties at p < .05.

TA B L E 4 Fatty acid composition in four varieties of chickpeas
There were significant differences in the USFA/SFA ratio between Muying-1 and Keying-1, Muying-1 and Desi-1, and Keying-1 and Desi-1 (p < .05), but there was no significant difference between Desi-1 and Desi-2. The USFA/SFA ratio of Keying-1 was the highest compared to the other samples. The fatty acid composition and high amounts of unsaturated fatty acids make chickpea a special legume, suitable for many nutritional applications.
The highest content of flavonoids in chickpeas was daidzein, with an average content of 3193.189 ng/g CCFE, accounting for 24.85% of the 46 total flavonoids, and the lowest content of flavonoids was icariin.
Muying-1 had a conjugate flavonoid concentration of 7189.5085 ng/kg CCFE and a free flavonoid concentration of 5659.3911 ng/kg CCFE. The conjugate flavonoid amount (55.95%) was higher than the amount of free flavonoids (44.05%). Many studies have focused on the hydrolysis of isoflavone glycosides, as isoflavone aglycones possess higher pharmaceutical activity than isoflavone glycosides (Izumi et al., 2000;Kawakami et al., 2005;Kaya et al., 2008). Isoflavone aglycones are absorbed more quickly in humans than their glycosides (Kawakami et al., 2005). However, isoflavone aglycones exist at low concentrations or are absent in leguminous plants. Yeom et al. (2012) determined the optimal pH and temperature for the conversion of genistin to genistein using β-glucosidase from Pyrococcus furiosus, and the hydrolytic activity and kinetic parameters of the enzyme for producing isoflavone F I G U R E 2 Total ion chromatograms (TICs) that were obtained for the detection and quantification of flavonoids in crude chickpea flavonoid extract (CCFE) TA B L E 5 The 46 flavonoids of Muying-1 chickpea using the internal standard method (IS method) by UPLC-QqQ-MS (ultra highperformance liquid chromatography coupled with triple quadrupole mass spectrometry)   3193.189, 1000.194, 1157.400, 15.759, and 12.174 ng/g, respec-tively. According to the literature, the total isoflavone content varied from 153 to 340 mg/100 g of chickpea and from 165 to 336 mg/100 g of soybean (Cantelli et al., 2017;Singh et al., 2017).

| CON CLUS IONS
In the present study, the chemical composition of the four chick- were 36.21, 36.22, 27.15, and 31.83 g/100 g, respectively. The protein content ranged from 19.79 to 23.38 g/100 g, and the four chickpea species were found to be rich in aspartic acid, glutamic acid, and arginine acid. The lipid contents in Muying-1, Keying-1, Desi-1, and Desi-2 were 8.39, 9.35, 6.65, and 6.35 g/100 g, respectively.
Chickpea seeds are characterized by a high content of the essential unsaturated fatty acids such as linoleic acid and oleic acid, as well as saturated fatty acids such as palmitic acid and stearic acid. Fortysix different flavonoids of Muying-1 chickpea were detected, corresponding to the UPLC-QqQ-MS analysis data. The results showed that isoflavones, such as daidzin, biochanin A, genistin, troxerutin, isorhamnetin, astilbin, L-epicatechin, astragalin, acacetin, hyperoside, and myricitrin, were the main flavonoids in Muying-1 chickpea.
Our findings highlighted the importance of chickpeas in the human diet and indicated that different types of chickpeas vary in nutritional and functional composition. Food processors should be aware of the different components among different chickpea species, which would be helpful to select specific species for better preparation of legume-based foods.

ACK N OWLED G M ENTS
This work was supported by the National Natural Science Foundation of China (No. 31960089) and Natural Science Foundation of Xinjiang (No. 2018D01C058).

CO N FLI C T O F I NTE R E S T
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.